Basic concepts of Bluetooth low energy true wireless twin speakers

To understand Bluetooth low energy, one should first understand how low power consumption is implemented in short-range wireless systems. Typically, one of the most basic design decisions is around typical use cases to achieve low power consumption. Bluetooth Low Energy is not meant to optimize classic Bluetooth, instead, it is aimed at emerging market segments that have not previously used open wireless standards. These market segments require devices to send data intermittently, with intervals ranging from seconds to days, and each data transmission consists of several bytes. They are typically monitoring or control applications used to perform tasks, such as detecting windows open or closed in smart home heating applications, switching appliances on and off based on floating electricity prices to switch to another TV channel, etc. www.bjbjaudio.com
time is energy
Time is energy is another fundamental concept that runs through the design of Bluetooth Low Energy. Once the radio starts working it needs to use energy, even just to check if it needs to send or receive. Therefore it becomes important to reduce the execution time of necessary operations. Many critical and repetitive operations must be optimized through measures, including robust device discovery, device connection, and data sending. By reducing the time required for these activities, energy consumption is reduced, thereby extending battery life. www.bjbjaudio.com

Robust device discovery requires at least two devices: one to find other devices, and one or more other devices to be discoverable. In Bluetooth Low Energy, a device must send three short messages every few seconds if it wants to be discovered: whereas if it wants to discover the device it intends to communicate with, the device should listen immediately after broadcasting the short message for other device, the device will turn on its receiver and listen for transmissions from other devices. www.bjbjaudio.com

The three transmissions are performed using three different frequencies to improve robustness. The choice of the number three is actually a balance between robustness and low power consumption: if the number of frequencies is only one, then as in many other techniques only that frequency is blocked . The whole system will not work. If the number of frequencies is too large, eg 16, the device will spend a lot of time transmitting. Will no longer be a "low power" device. www.bjbjaudio.com

Careful consideration should also be taken when choosing which devices to transmit and which  to receive. Searching for a transmitting device can take a long time and therefore consume a lot of energy, so such operations should be left to devices with more energy reserves or just choose low-power devices. In Bluetooth Low Energy, discoverable devices perform transmission of data. And devices looking for other devices perform reception. www.bjbjaudio.com 

The length of the datagram is very short, mainly for the following three reasons: First, by using high-efficiency encoding. Short packets can send the same amount of data faster using less energy. Second, the device is restricted to use only short messages . The controller eliminates the need to constantly calibrate the radio during a data transfer. This is due to the fact that the radio module constantly heats up when transmitting or receiving, which will change the characteristics of the silicon chip and therefore the transmission frequency. If the message is controlled in a short length, the chip does not have enough time to heat up, so the offset of the transmission frequency can be ignored. In addition, the requirement for short messages also slightly reduces the peak power of the chip. Finally , short-term, intermittent rather than long-term, continuous power draws allow devices to draw more power from a single coin cell battery. It can be seen that compared with the solution of lo ng messages, the solution of using short messages and leaving enough space between them to allow the battery to recover is more suitable.
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